Patent claim interpretation: a flash of excitement?

The boring subject of patent claim interpretation: a flash of excitement or just more academic overreaction?

Earlier this year the New Zealand Court of Appeal presented the latest judgment* in a long line of cases in both New Zealand and overseas dealing with the issue of patent claim interpretation. Although relatively brief in terms of its analysis of the relevant legal principles, the case provides significant guidance as to the approach likely to be taken by New Zealand courts in the future and, in particular, resolves potential ambiguity in earlier decisions as to the significance of the specification to the interpretation of the claims. This article provides a brief summary of the nature of a patent specification and the claims, looks at the historic approach to claim interpretation, the current test, and then examines the approach by the Court of Appeal in Hammar Maskin in order to illustrate the way in which that test is likely to be practically applied in future cases.

The nature and content of a patent specification

The purpose of a patent specification is to describe, in words which would be understood to a skilled reader, the nature of the invention protected. As the grant of a patent is a social contract (in which the patentee is awarded a 20 year monopoly in return for increasing the pool of knowledge available to others) the specification must contain a complete description of the invention and the best method of putting the invention into practice known to the patentee at the time the specification is filed.

Specifications are broadly divisible into the description or consistory clauses (Sections 10(1) and (3)(a) of the Patents Act), the best method of performing the invention (Section 10(3)(b)) and the claims (Sections 10(3)(c) and (4)).

Claims and claim interpretation

It is well settled that the function of claims is to "define clearly and with precision the monopoly for which protection is sought, so that others may know the exact boundaries of the area within which they will be trespassers": EMI Ltd v Lissen Ltd (1938) 56 RPC 23, 39 (HL).

It is therefore the claims which define the scope of the invention. This can be important for two purposes: firstly, when determining the validity of a patent specification during examination or opposition (pre-grant), or revocation (post-grant); and secondly for the purposes of determining infringement. The rules of claim interpretation are inelastic in the sense that they are the same for determining infringement as they are for validity. A brief historical analysis of those rules follows.

Until the early 1980's it was generally accepted that words and grammar of patent claims (and indeed any other legal document) should be given their "natural and ordinary meaning". Thus, meanings would be assigned to the words by dictionary and to the syntax by ordinary rules of grammar, and this approach would be adopted regardless of the context or background against which the words were used unless they were ambiguous. Consistent with this, in EMI Ltd v Lissen Ltd (1938) 56 RPC 23, 57 (HL) it was stated:

"If the claims have a plain meaning in themselves [emphasis added], then advantage cannot be taken of the language used in the body of the specification to make them mean something different."

In the case of ambiguity only, the court could have regard to the context provided by the specification and drawings. If that was insufficient to resolve the ambiguity, the court could have regard to other extrinsic evidence which would have been in the knowledge of the author when he wrote the patent document.

Rigorously applied, these rules would mean that, unless the court could find some ambiguity in the language of the claims, they might be construed in a sense which a reasonable reader, understanding the context and background to the patent, would never have thought the author intended. Therefore, there are numerous examples in early case law of courts finding ambiguity in otherwise clear claim language so as to reach the right result.

A step change occurred in the early 1980's with the case of Catnic Components v Hill & Smith Ltd (1982) 99 RPC 185 (HL). In this case Lord Diplock advocated a new approach to the construction of patent claims in which:

"A patent specification should be given a purposive construction rather than a purely literal one derived from applying to it the kind of meticulous verbal analysis in which lawyers are too often tempted by their training to indulge."

This became known as the doctrine of "purposive" construction.

The doctrine of purposive construction

The doctrine, while simple in principle, has proven complicated in application. That is because construction of a patent is not concerned with what the author meant to say. Construction is objective in the sense that it is concerned with what a reasonable person would have understood the author to be saying. The line between the two has always been a grey one, not helped by some of the more eminent judicial minds themselves straying. For example, in Rockwater Ltd v Technip France SA [2004] EWCA CIV 38 Jacob LJ held (at para 41(e)) that to be "fair to the patentee" one must use "the widest purpose consistent with his teaching" and thus confused the purpose of the patent with what it would be understood to mean. The purpose of a patent specification is simply to communicate an idea in concise terms. An appreciation of the purpose is part of the factors which one uses to ascertain meaning but they are not the same thing. There is no presumption about the width of claims. A patent may, for one reason or another, claim less than it teaches or enables.

Other courts have experienced difficulties in restating the test leading to further ambiguity as to the significance of the specification to the claims. In Glaverbel SA v British Coal Corp. (1995) 112 RPC 255, the House of Lords summarised the principles of purposive construction as including that:

• The court should have regard to the surrounding circumstances at the date of publication (or perhaps the priority date) but only insofar as those facts would be available to "every skilled addressee";
• The patent specification must be read together with the claims; and
• Any claim must be construed in the context of the patent as a whole, but a claim "expressed in clear language…cannot be extended or cut down by reference to the rest of the specification".

This last point would seem to affirm the principle in EMI v Lissen that a claim worded plainly and in easily understandable terms cannot be modified by reference to the body of the specification - although the House of Lords added (somewhat enigmatically) that the purposes of the author of the specification can be used to determine the meaning of the document.

Picking up on this, the New Zealand High Court in Lucas v Peterson Portable Sawing Systems [2003] 3 NZLR 361 held that:

• The specification is to be interpreted as a whole. Since it is the claims that define the scope of the monopoly, they will normally be the starting point but ambiguity in words or expressions can, in appropriate cases, be resolved by reference to the context of the document as a whole. Importantly, for this purpose, the document includes the drawings; and
• When referring to the body of the specification for the purposes of clarifying ambiguous expressions in a claim, consistory clauses may be exhaustive as to the intended scope of the expression. Embodiments, on the other hand, might help to show the broadness of a claim but presumably never its narrowness.

Once again this would seem to advocate reference to the body of the specification only in the case of ambiguity.

However, the New Zealand Supreme Court, while not taking issue with the approach of the High Court, made the following additional observations on appeal ([2006] 3 NZLR 721 (SC) at paragraphs 26-28):

"Each part of the patent specification is to be read objectively in its overall context and in light of the function of that part. The claims are to be interpreted by reference to the object and description in the body of the specification…

The claims define the scope of the monopoly conferred by the patent. They limit what others may do. They must clearly define the protected field so others may fairly know where they cannot go. The description in the body of the specification may assist interpretation but it cannot modify the monopoly the inventor has clearly marked out. If this claim is formulated too narrowly so that imitators do not infringe, that cannot be rectified by reference to the description. If it is too wide, consequent invalidity cannot be saved by reading in limitations appearing in the description."

So where does that leave us?

Attempting to reconcile all of the above appears to leave an internal inconsistency in certain of the tests advocated regarding the effect on the claims of information appearing in the body of the specification. On the one hand, the tests seem to advocate that infringement should be determined by reference to the claims and, while it is permissible to look to the body of the specification solely to resolve ambiguity, even in those cases poor claim drafting cannot be saved by favourable references in the specification (per the tests advocated in Glaverbel and the High Court in Lucas). This approach would seem to suggest that where the meaning of the claims is clear, infringement should be determined solely by reference to the claims.

On the other hand there is a clear reference to the requirement to read the claims in conjunction with the specification and to construe them in the context of the patent and by reference to the object and description in the body of the specification (again per Glaverbel and the Supreme Court decision in Lucas).

The ambiguity is resolved to some extent by Lord Hoffman in Kirin-Amgen, Inc v Hoechst Marion Roussel Ltd [2004] UKHL 46. When describing the legal climate prior to Catnic (and the consequent doctrine of purposive construction) his Lordship said:

"It came to be recognised that the author of a document such as a contract or patent specification is using language to make a communication for a practical purpose in that a rule of construction that gives his language a meaning different from the way it would have been understood by the people to whom it was actually addressed is liable to defeat his intentions."

In other words, while the starting premise must be that interpretation is governed by the claim and, therefore, if there is no ambiguity in the wording of the claims, it is possible for the court to make a prima facie assessment of infringement, as the claims must be read in the context of the specification, following that exercise the court must stand back and ask whether the interpretation of the claims which has been applied (ie the meaning), and the result which has been reached, is reasonable having regard to the purpose of the patent specification.

Case example: Hammar Maskin AB & Others v Steelbro New Zealand Limited

This approach is perhaps best illustrated by reference to an example. In Hammar Maskin AB & Others v Steelbro New Zealand Limited [2010] NZCA 83 the question was whether the defendant, Steelbro, had infringed a patent directed to a stabiliser for a side-lifting container trailer. The claims of that patent required, in part, that the stabiliser mechanism incorporate a support sleeve and an extension part which was said to be "moveably arranged in a bearing" in the support sleeve.

After hearing from experts for both parties, Panckhurst J held (in the High Court#) that the description can only be read as referring to an additional element which performs the function of a bearing and, as Steelbro's stabiliser did not have that additional component, it could not infringe the claims. Hammar appealed, arguing that the word "bearing" in claim 1 was intended to convey the concept of a "state of bearing" rather than a discrete physical component. Hammar relied, in part, on the fact that, despite the word "bearing" appearing in claim 1, there was no reference to a "bearing" in the form of a discrete physical component in either the description of the prior art or the detailed description of the invention which appeared in the specification. In response, Steelbro argued that, as the meaning of the claim was clear on its face (ie there was no ambiguity) no reference could be made to the body of the specification.

The Court of Appeal rejected that submission, relying upon the Supreme Court's test in Lucas which requires the claims to be interpreted in the overall context and by reference to the object and description in the body of the specification. Thus, while the Court of Appeal agreed that the phrase "in a bearing" in isolation from its context might more naturally denote a separate physical component, interpreted in the context of the specification as a whole, that phrase could only refer to "bearing" in a functional sense.

The last word...?

It is understood that Steelbro has sought leave to appeal the Court of Appeal's decision to the Supreme Court, so this may not be the last word on claim interpretation from our appeal courts. Watch this space.

*Hammar Maskin AB & Others v Steelbro New Zealand Limited [2010] NZCA 83
#Hammar Maskin AB & Others v Steelbro New Zealand Ltd HC Christchurch CIV 2006-409-0977, 8 October 2008

By Ian Finch, Partner

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